The Aurora Gloriousia was a location in the fourth universe. The Blitzen fish were native to the area. (AUDIO: Relative Dimensions)
After a seven metre, dormant Blitzen fish was awoken in the TARDIS, it began to jump from plane to plane, and also through time. The Eighth Doctor, with the help of Lucie Miller, Alex and Susan Campbell, managed to release the fish back into the Aurora Gloriousia where it could no longer do harm. (AUDIO: Relative Dimensions)